Lung cancer risk in past asbestos workers a few decades after exposure cessation and prospects for screening

Our plain-English summary of Lung cancer risk in past asbestos workers a few decades after exposure cessation and prospects for screening, by G. Mastrangelo, G. Marangi, M.N. Ballarin, et al (Archives of Environmental & Occupational Health, 2016).

The study

• Authors: G. Mastrangelo, G. Marangi, M.N. Ballarin, E. Fadda, L. Scoizzato, U. Fedeli, L. Marchiori, F. Valentini
• Journal: Archives of Environmental & Occupational Health
• Published: 2016;71(4):237-44
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To ascertain whether the current risk of lung cancer in former asbestos workers was higher than in the general population, 1,557 past asbestos workers were recruited during statutory health examinations (from 2000 onward) and followed up for mortality. Standardized mortality ratios (SMRs) were calculated. Poisson regression was used to adjust the rate ratios (RRs) for confounders. SMR was about 1.00 in workers with or without pleural plaques and 4.62 (95% confidence interval: 0.61-18.1) in those with asbestosis. Adjusted RRs for lung cancer were 4.70 (0.99-22.5) for asbestosis, 4.35 (0.97-19.5) for former smokers, 6.82 (1.38-34.4) for current smokers. Currently, lung cancer mortality in past asbestos workers is similar to the general population, probably because workers more exposed /more susceptible could have died from lung cancer before the beginning of follow-up.

In plain English

This Italian cohort mortality study asked whether former asbestos workers still had a higher risk of dying from lung cancer than the general population one or more decades after their exposure ended. It included 1,557 men who had health examinations in Veneto from 2000 onward. Their past asbestos exposure was estimated from questionnaires, and deaths were tracked to the end of 2010. Twenty died from lung cancer. Lung cancer deaths were close to the expected regional level both in workers with pleural plaques only and in those with no asbestos disease. In workers with asbestosis, the standardized mortality ratio was 4.62 (95% confidence interval 0.61 to 18.1). That figure rested on two deaths and was not statistically significant. In the fully adjusted analysis, rate ratios were 4.70 (0.99 to 22.5) for asbestosis and 6.82 (1.38 to 34.4) for current smokers. The authors concluded that lung cancer risk had fallen to the regional level a few decades after exposure ended. They cautioned that survival bias may explain this, since more-exposed or more-susceptible workers may have died before follow-up began.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Cohort mortality study (time-based cohort of workers alive in 2000), with external comparison to the regional population (standardized mortality ratios) and internal comparison using Poisson regression
• Who was studied: 1,557 male former asbestos workers (from an initial 1,700; women and workers examined in 2011 excluded). They were examined from 2000 onward at 21 occupational health and safety departments (SPISAL) in Veneto, northeastern Italy, and followed for mortality until 31 December 2010.
• Exposure: Past occupational asbestos exposure; the article does not specify fiber types for the cohort. Cumulative exposure was estimated retrospectively by questionnaire for 1,484 workers. The mean was 159.6 (standard deviation 187.5) ff/ml-years, analysed in tertiles: 0.001 to 49.67, 50.14 to 247.5, and 250.3 to 3300. Mean time since last exposure was 16.2 years.
• Main results:
  • Of the 1,557 workers, 756 had benign asbestos disease (724 with pleural plaques only and 32 with asbestosis). The other 801 had no benign asbestos disease.
  • Twenty workers died from lung cancer between 2000 and 2010: 11 in the group with pleural plaques or asbestosis and 9 in the group without asbestos disease.
  • Compared with the general population of Veneto, the SMR was 1.05 (95% CI 0.46 to 1.92) in workers with pleural plaques only and 1.05 (0.48 to 1.99) in workers with no asbestos disease.
  • In workers with asbestosis, the SMR was 4.62 (95% CI 0.61 to 18.1). It was based on 2 observed deaths against 0.4 expected and was not statistically significant.
  • In the fully adjusted Poisson model (Model 2), the rate ratios for lung cancer were as follows. Asbestosis: 4.70 (0.99 to 22.5), p = 0.052, versus workers with no asbestos disease. Current smokers: 6.82 (1.38 to 34.4), p = 0.018, versus nonsmokers. Former smokers: 4.35 (0.97 to 19.5). Pleural plaques: 0.93 (0.35 to 2.45). Cumulative exposure, middle and highest tertiles versus lowest: 1.55 (0.52 to 4.61) and 1.47 (0.44 to 4.89). The authors stated that only asbestosis and current smoking significantly increased lung cancer mortality.
  • No statistically significant interaction was found between smoking and asbestos exposure.
• The authors' conclusion: The authors concluded that the risk of death from lung cancer had fallen to the level of the regional population a few decades after asbestos exposure ended. They said further studies are needed to assess whether high-risk subgroups, possibly workers who developed asbestosis, could benefit from low-dose CT screening.
• Limitations the authors state:
  • The cohort was fairly small and the follow-up period short.
  • Smoking status was recorded only once, at enrollment, so later changes in smoking habits could cause misclassification.
  • Asbestosis may have been misclassified.
  • All cohort members were alive in 2000, so the lack of association between asbestos and lung cancer could reflect survival bias. More-exposed or more-susceptible workers may have died from lung cancer before follow-up began. The authors said this prevents conclusions about asbestos exposure variables, including cumulative exposure, and lung cancer risk.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Lung Cancer, standardized mortality ratio (SMR), rate ratio, Pleural Plaques, confidence interval.

Related studies

• Feasibility of a screening programme for lung cancer in former asbestos workers — G. Mastrangelo, M.N. Ballarin, et al. (2008)
• Yield of Low-Dose Computerized Tomography Screening for Lung Cancer in High-Risk Workers: The Case of 7189 US Nuclear Weapons Workers — S.B. Markowitz, A. Manowitz, et al. (2018)
• Cancer risk after cessation of asbestos exposure: a cohort study of Italian asbestos cement workers — C. Magnani, D. Ferrante, et al. (2008)
• The costs and effects of screening for cancer among asbestos-exposed workers — B.J. McNeil, D.M. Eddy (1982)
• Urinary asbestos fibers and inorganic particles in past asbestos workers — S. Zaina, G. Mastrangelo, et al. (2016)
• Screening for lung cancer in a high-risk group: but I still haven't found what I'm looking for — G.A. Silvestri (2007)

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